This application is related to co-pending application Ser. No. 08/270,563 entitled "Translucent Fluorescent Filter For Display Panels", filed concurrently with this application which is incorporated herein by reference.
The present invention relates in general to electroluminescent lamp panels, and more specifically to the use of fluorescence to modify the color spectrum of light emitted by the electroluminescence of the lamp panel.
An electroluminescent (EL) panel typically comprises a microencapsulated phosphor contained between two conductive plates. One plate is transparent to pass light generated when the plates are charged with an AC voltage. EL has advantages of small size (it is very thin) and an ability to selectively backlight desired areas of control panels without complicated light baffles or light pipes. One limitation of EL is that its luminance level or brightness tends to be lower than that achievable with other sources unless high voltage levels or frequencies are applied. Furthermore, the brightness achievable at a particular voltage and frequency depends on the color of light produced. Phosphors formulated for producing blue light have achieved higher brightness than for other colors (especially red) or blends of colors. Thus, brightness from an EL lamp panel has been approximately directly proportional to the frequency of light produced.
Although brightness can be generally increased by applying a higher voltage or a higher frequency to the EL lamp panel, voltage is limited in automotive systems unless expensive converters are used. Higher voltages also create more stress in the phosphor layer, reducing the lifetime and durability of the EL lamp. In addition, higher frequencies are undesirable because of increased electromagnetic radiation.
In view of the foregoing factors, lamp durability, brightness, and the colors of light obtainable have been subject to various trade-offs.